Heat pump water heater appliance

ABSTRACT

Water heater appliances and methods for operating water heater appliances are provided. A water heater appliance includes a tank defining an interior volume, and a sealed system for heating water within the interior volume. The sealed system includes a compressor operable to compress refrigerant, a first condenser downstream of and in fluid communication with the compressor, and a second condenser downstream of and in fluid communication with the compressor. The first and second condensers are each operable to heat water within the interior volume using energy from the refrigerant. The sealed system additionally includes a valve in fluid communication with the first and second condensers and configured to vary a ratio of refrigerant flow through the first and second condensers.

FIELD OF THE INVENTION

The present subject matter relates generally to water heater appliances, such as heat pump water heater appliances, and methods for operating the same.

BACKGROUND OF THE INVENTION

Certain water heaters operate such that water within the water heater's tank is heated to a set temperature. Generally, a user can select the set temperature using a dial or other input on the water heater. Heat pump water heaters are gaining broader acceptance as a more economic and ecologically-friendly alternative to electric water heaters. Heat pump water heaters include a sealed system for heating water to the set temperature. The set temperature is generally selected such that heated water within the tank is suitable for showering, washing hands, etc.

A typical sealed system includes a compressor, a condenser, an expansion device, and an evaporator operating in a closed loop to manipulate a refrigerant. The condenser may be positioned adjacent to the tank of the water heater and the refrigerant flowing through may in turn exchange energy with water in the tank of the water heater, heating the water.

Typical heat pump water heaters position the condenser adjacent to a bottom end of the tank so as to heat the cooler water at the bottom of the tank and provide a more uniformly heated tank of water. However, water may be drawn from a top end of the tank. Accordingly, during events demanding high volumes of hot water, the sealed system of the heat pump water heater may not have time to fully and uniformly heat the water within the tank.

In certain heat pump water heaters, supplemental electrical resistance heaters may be included to provide additional heating for the water in the tank during such high demand conditions. However, certain problems may exist with such a configuration. For example, the additional energy required for the supplemental heater may create an inefficient design for heating the water in the tank. Accordingly, a water heater that may provide relatively efficient supplemental heating would be useful.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention are set forth below in the following description, or may be obvious from the description, or may be learned through practice of the invention.

In one exemplary embodiment of the present disclosure, a water heater appliance is provided. The water heater appliance includes a tank defining an interior volume and a sealed system for heating water within the interior volume of the tank. Additionally, the sealed system includes a compressor operable to compress a refrigerant, a first condenser positioned downstream of and in fluid communication with the compressor, and a second condenser also positioned downstream of and in fluid communication with the compressor. The first and second condensers are each operable to heat water within the interior volume of the tank using energy from the refrigerant. The sealed system also includes a valve in fluid communication with the first condenser and the second condenser and configured to vary a ratio of refrigerant flow through the first condenser and through the second condenser.

In one exemplary aspect of the present disclosure, a method is provided for operating a water heater appliance. The method includes flowing a refrigerant through a compressor and flowing a first portion of the refrigerant from the compressor through a first condenser operable to heat water within an interior volume of a tank of the water heater appliance. The method also includes flowing a second portion of the refrigerant from the compressor through a second condenser operable to heat water within the interior volume of the tank of the water heater appliance. Additionally, the method includes varying a ratio of refrigerant flow through the first condenser and through the second condenser using a valve in fluid communication with the first condenser and the second condenser.

These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures.

FIG. 1 provides a perspective view of a water heater appliance in accordance with one embodiment of the present disclosure.

FIG. 2 provides a schematic view of certain components of the exemplary water heater appliance of FIG. 1.

FIG. 3 provides a flow diagram of a method of operating a water heater appliance in accordance with an exemplary aspect of the present disclosure.

DETAILED DESCRIPTION

Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

Referring now to the drawings, FIG. 1 provides a perspective view of a water heater appliance 100 according to an exemplary embodiment of the present disclosure; and FIG. 2 provides a schematic view of the exemplary water heater appliance 100 of FIG. 1. The water heater appliance 100 depicted includes a casing 102 and a tank 112 positioned at least partially within the casing 102 (FIG. 2). More particularly, as is shown schematically in FIG. 2, the exemplary tank 112 is mounted completely within the casing 102 and defines an interior volume 114 for storing and heating water positioned therein. Additionally, the tank 112 of the water heater appliance 100 includes an upper portion 154 and a lower portion 156, each defined along a vertical direction V (FIG. 2). The upper portion 154 is thus generally above the lower portion 156 along the vertical direction V.

The water heater appliance 100 extends between a top 108 and a bottom 109 along the vertical direction V. Thus, the water heater appliance 100 is generally vertically oriented. The water heater appliance 100 may be leveled, e.g., such that the casing 102 is plumb in the vertical direction V, in order to facilitate proper operation of the water heater appliance 100.

A drain pan 110 is positioned adjacent to the bottom 109 of the water heater appliance 100 such that water heater appliance 100 sits on the drain pan 110 (FIG. 1). The drain pan 110 sits beneath the water heater appliance 100 along the vertical direction V, e.g., to collect water that leaks from the water heater appliance 100 or water that condenses on an evaporator 130 of the water heater appliance 100. It should be understood, however, that the water heater appliance 100 is provided by way of example only and that the present subject matter may be used with any suitable water heater appliance.

Referring now specifically to FIG. 2, the water heater appliance 100 includes a cold water conduit 104 and a hot water conduit 106 that are both in fluid communication with the tank 112. As an example, cold water from a water source, e.g., a municipal water supply or a well, enters water heater appliance 100 through cold water conduit 104. From the cold water conduit 104, such cold water enters the interior volume 114 of the tank 112 wherein the water is heated to generate heated water. Such heated water exits the water heater appliance 100 at the hot water conduit 106 and, e.g., is supplied to a bath, shower, sink, or any other suitable feature.

The cold water conduit 104 and hot water conduit 106 each extend into the interior volume 114. For the exemplary embodiment of FIG. 2, the cold water conduit 106 defines a length 105 along the vertical direction V within the interior volume 114 and the hot water conduit 106 defines a length 107 along the vertical direction V within the interior volume 114. In the exemplary embodiment depicted, the length 105 of the cold water conduit 104 within the interior volume 114 is greater than the length 107 of the hot water conduit 106 within the interior volume 114.

The water heater appliance 100 includes a sealed system 120 for heating water within the interior volume 114 of the tank 112. The sealed system 120 generally operates in a heat pump cycle. Thus, the water heater appliance 100 is commonly referred to as a “heat pump water heater appliance.” Although not depicted for the exemplary embodiment of FIG. 2, the water heater appliance 100 may additionally include one or more auxiliary heating elements.

The sealed system 120 includes a compressor 122, a first condenser 124, and a second condenser 126. The compressor 122 may be operable to compress the refrigerant. Accordingly, the pressure and temperature of the refrigerant may be increased in the compressor 122 such that the refrigerant becomes a superheated vapor. The superheated vapor may then flow to one or both of the first and second condensers 124, 126, as will be explained in greater detail below. More particularly, as is depicted, the first condenser 124 is positioned downstream of and in fluid communication with the compressor 122, and may be operable to heat the water within the interior volume 114 using energy from the refrigerant. For example, the superheated vapor from compressor 122 may enter the first condenser 124 wherein it transfers energy to the water within tank 112 and condenses into a saturated liquid and/or liquid vapor mixture. Similarly, the second condenser 126 is also positioned downstream of and in fluid communication with the compressor 122, and may also be operable to heat the water within the interior volume 114 using energy from the refrigerant, such as by condensing the refrigerant. As will be discuss in greater detail below, the first condenser 124 is configured in parallel flow with the second condenser 126.

For the exemplary embodiment of FIG. 2, each condenser 124, 126 is assembled in a heat exchange relationship with tank 112 in order to heat water within the interior volume 114 of tank 112 during operation of sealed system 120. More particularly, for the exemplary embodiment of FIG. 2, the first condenser 124 and the second condenser 126 are depicted being in thermal communication with the tank 112 by being wrapped around and surrounding the tank 112, such as in a generally helical manner. It should be appreciated, however, that in other exemplary embodiments, the first condenser 124 and/or the second condenser 126 may have any other configuration suitable for exchanging heat with water in the interior volume 114 of the tank 112. For example, in certain alternative embodiments, at least a portion of one or both of the first condenser 124 and second condenser 126 may be positioned within the interior volume 114 of the tank 112.

Referring still to FIG. 2, the exemplary sealed system 120 further includes an expansion device 128 and an evaporator 130. The expansion device 128 is positioned downstream from and in fluid communication with the first condenser 124 and the second condenser 126, and the evaporator 130 is positioned downstream from and in fluid communication with the expansion device 128. Refrigerant, which may be in the form saturated liquid vapor mixture, may for example exit one or both of the first condenser 124 and the second condenser 126 and travel through the expansion device 128. The expansion device 128 may generally expand the refrigerant, lowering the pressure and temperature thereof before the refrigerant flows to and through the evaporator 130. The expansion device 128 may be any suitable component for generally expanding the refrigerant. For example, in certain exemplary embodiments the expansion device 128 may be a Joule-Thomson effect valve, a capillary tube valve, or any other suitable valve.

The evaporator 130 is, in turn, positioned upstream from and in fluid communication with the compressor 122. During operation of the sealed system 120, refrigerant may flow from the evaporator 130 back to and through the compressor 122 and restart the heating cycle of the sealed system 120. Notably, the sealed system 120 depicted in FIGS. 1 and 2 is positioned in the casing 102 of the water heater appliance 100. More particularly, for the exemplary embodiment of FIGS. 1 and 2 the compressor 122, the first and second condensers 124, 126, the expansion device 128, and the evaporator 130 are each positioned within the casing 102 of the water heater appliance 100. Although such a configuration may increase the convenience of the water heater appliance 100, in other exemplary embodiments, one or more of the various components in the sealed system 120 may alternatively be positioned outside of and/or adjacent to the casing 102.

As is also depicted in FIG. 2, various conduits may be utilized to flow the refrigerant between the various components of the sealed system 120. For example, a conduit 140 is utilized to flow refrigerant from the evaporator 130 to the compressor 122, a conduit 142 is utilized to flow refrigerant from the compressor 122 to one or both of the first condenser 124 and the second condenser 126, a conduit 144 is utilized to flow refrigerant from one or both of the first condenser 124 and the second condenser 126 to the expansion device 128, and a conduit 146 is utilized to flow refrigerant from the expansion device 128 to the evaporator 130.

Moreover, as stated, the first condenser 124 is configured in parallel flow with the second condenser 126. Accordingly, the sealed system 120 defines a first upstream joint 136 configured to provide fluid communication from the conduit 142 to the first condenser 124 and the second condenser 126. Similarly, the sealed system 120 additionally defines a second downstream joint 138 configured to provide fluid communication from the first condenser 124 and the second condenser 126 to the conduit 144.

Referring still to the exemplary embodiment of FIG. 2, the second joint 138 comprises a valve 158 in fluid communication with the first and second condensers 124, 126 and positioned downstream from the first and second condensers 124, 126. More particularly, the valve 158 includes a first port 164 in fluid communication with the first condenser 124, a second port 166 in fluid communication with the second condenser 126, and a third port 168 in fluid communication with the expansion device 128 through the conduit 144. As the valve 158 is positioned downstream from the first and second condensers 124, 126, the refrigerant flowing through may be at a temperature less than a temperature of the refrigerant at, e.g., the joint 136 immediately upstream of the first and second condensers 124, 126. Additionally, a velocity of the refrigerant through the valve 158, i.e., at a point downstream of the condensers 124, 126, may be lower than the velocity of the refrigerant upstream of the condensers 124, 126 (e.g., at the upstream joint 136). This is due to the fact that the refrigerant may be in a superheated vapor condition at the upstream joint 136, while the refrigerant may be in a liquid condition at the downstream joint 138 (and thus may be more dense). Accordingly, such a configuration may therefore reduce an amount of wear on the valve 158 during operation of the sealed system 120 and increase the working lifespan of the valve 158.

It should be appreciated, however, that the exemplary embodiment depicted in FIG. 2 is by way of example only. In other exemplary embodiments, for example, the valve 158 may instead be positioned upstream from the first condenser 124 and the second condenser 126, such that the joint 136 comprises the valve 158 and the third port 168 is instead in fluid communication with the compressor 122 through the conduit 142.

The valve 158 is configured to vary a ratio of refrigerant flow through the first condenser 124 and through the second condenser 126 to increase the heating times and/or efficiency of the water heater appliance 100. The ratio of refrigerant flow through the first condenser 124 and through the second condenser 126 may be expressed as an R₁:R₂ value. For example, an amount R₁ may correspond to an amount of refrigerant that flows through the first condenser 124 and an amount R₂ may correspond to an amount of refrigerant that flows through the second condenser 126. Moreover, the valve 158 may be capable of varying the ratio of refrigerant flow from an R₁:R₂ value of 0:100 to an R₁:R₂ value of 100:0, and any ratio therebetween. When, for example, the ratio of refrigerant flow is set by the valve 158 to an R₁:R₂ value of 0:100, all of the refrigerant flow from the compressor 122 is directed through the second condenser 126 and the second condenser 126 thus provides substantially all of the heat from the sealed system 120 to the tank 112 proximate to the lower portion 156 of the tank 112. By contrast, when, for example, the ratio of refrigerant flow is set by the valve 158 to an R₁:R₂ value of 100:0, all of the refrigerant flow from the compressor 122 is directed through the first condenser 124 and the first condenser 126 thus provides substantially all of the heat from the sealed system 120 to the tank 112 proximate to the upper portion 154 of the tank 112. As used herein, terms such as “approximately” and “substantially” refer to being within a 10% margin of error.

The valve 158 may be any type of valve capable of varying the ratio of refrigerant flow through the first port 164 and the second port 166. For example, the valve 158 may be what is commonly referred to as a “three-way valve,” such as a Y-valve, a T-valve, or any other type of variable flow splitting valve. Moreover, the valve 158 may be a purely mechanical valve or alternatively may be an electromechanical valve. For example, the valve 158 may utilize a stepper motor that requires electrical energy to move positions and vary the ratio of refrigerant flow, but does not require energy to maintain the valve 158 in position.

The use of two condensers 124, 126 in the sealed system 120 may provide more efficient supplemental heating of the water in the interior volume 114 of the tank 112 during events demanding high volumes of hot water from the water heater appliance 100. More particularly, by using a single sealed system 120 capable of varying the ratio of refrigerant flow between the first condenser 124 and the second condenser 126, the water heater appliance 100 may operate more efficiently and may be better suited for meeting high volume demands for hot water. Additionally, use of a single valve 158 to vary the ratio of refrigerant flow between the first and second condenser 124, 126 may allow for use of dual condensers without the need for separate valves associated with each condenser. Accordingly, the use of the single valve 158 to vary the ratio of refrigerant flow between the first and second condenser 124, 126 may allow for the use of dual condensers without the need for an electrically actuated solenoid valve, which may in certain embodiment create an undesirable amount of sound when activated.

For example, the configuration of the sealed system 120 of the water heater appliance 100 may take into consideration temperature gradients within the interior volume 114 of the tank 112 and the position of the hot water conduit 106 within the interior volume of the tank 112. For example, a temperature gradient may exist during operation of the water heater appliance 100 when hot water is being drawn from the tank 112 through the hot water conduit 106 and when cold water is flowed into the tank 112 through the cold water conduit 104. The temperature gradient may exist along the vertical direction V. Hotter water may be located towards the top 108, such as in the upper portion 154, above colder water which may be located towards the bottom 109, such as in the lower portion 156. The hot water conduit 106 is therefore positioned to take water from the upper portion 154 of the tank 112. The second condenser 126 is positioned to provide heat to the lower water temperatures at the lower portion 156 of the tank 112.

An illustrative embodiment will now be discussed. During operation of the water heater appliance 100 wherein a relatively low volume demand for hot water is present, the second condenser 126 may have time to sufficiently heat the water in the interior volume 114 of the tank 112 from the lower portion 156, such that a minimal temperature gradient is present. In such an embodiment the valve 158 may define an R₁:R₂ value of 0:100, such that the second condenser 126 provides substantially all of the heat to the tank 112 proximate to the lower portion 156 of the tank 112.

However, in certain cases, such as times when there is a relatively high volume of hot water demanded from the appliance 100, the second condenser 126 may not be configured to efficiently heat the water in the lower portion 156 of the tank 112 quickly enough to keep up with the demand. Accordingly, the first condenser 124 is positioned to provide heat to water within the interior volume 114 of the tank 112 at the upper portion 154 of the tank 112. Therefore, during events wherein, e.g., there is a high volume of hot water demanded from the appliance 100, the valve 158 may define an R₁:R₂ value of approximately 50:50, such that the first and second condensers 124, 126 each provide heat to the tank 112 along the vertical direction V of the tank 112. However, in other exemplary embodiments, the valve 159 may instead define an R₁:R₂ value of, e.g., approximately 100:0 such that the first condenser 124 provides substantially all of the heat to the tank 112 proximate the upper portion 154 of the tank 112 (and proximate the hot water conduit 106).

In certain exemplary embodiments, the first condenser 124 may thus be positioned above the second condenser 126 along the vertical direction V. More particularly, for the exemplary embodiment of FIG. 2, the first condenser 124 surrounds the upper portion 154 of the tank 112 and the second condenser 126 surrounds the lower portion 156 of the tank 112. Such positioning of the condensers 124, 126 may advantageously facilitate improved interaction with water in the interior volume 114, such as water at varying temperatures, thus improving the efficiency and increasing the energy costs of the system 120 and appliance 100 in general.

It should be appreciated, however, that in other exemplary embodiments, the water heater appliance 100 may be operated in any other suitable manner. For example, in other exemplary embodiments, the water heater appliance 100 may be operated in a “low demand” mode. The low demand mode may be, for example, when the appliance 100 is utilized by a single person (as opposed to an entire household), wherein only a portion of a capacity of the appliance 100 is needed. During the low demand mode, the first condenser 124 may be used to heat just the upper portion 154 of the tank 112 to provide the necessary amount of hot water. Such a configuration may minimize a “standby” energy loss.

Referring still to the exemplary embodiment depicted in FIG. 2, the water heater appliance 100 may additionally include a temperature sensor 152. The temperature sensor 152 may be configured for measuring a temperature of water within interior volume 114 of tank 112. The temperature sensor 152 may be positioned at any suitable location within water heater appliance 100. For example, temperature sensor 152 may be positioned within interior volume 114 of tank 112 or may be mounted to tank 112 outside of interior volume 114 of tank 112. The temperature sensor 152 may further be positioned proximate to the upper portion 154 of the tank 112 to measure the temperature of the water that has been heated by the first and/or second condenser 124, 126. When mounted to the tank 112 outside of the interior volume 114 of the tank 112, the temperature sensor 152 may be configured for indirectly measuring the temperature of water within the interior volume 114 of tank 112. For example, temperature sensor 152 may measure the temperature of tank 112 and correlate the temperature of tank 112 to the temperature of water within interior volume 114 of tank 112. Temperature sensor 152 may be any suitable temperature sensor. For example, temperature sensor 152 may be a thermocouple or a thermistor. Moreover, in other exemplary embodiments, the water heater appliance 100 may additionally include a plurality of temperature sensors 152 positioned at any suitable location.

Water heater appliance 100 may further include a controller 150 that regulates operation of water heater appliance 100. The controller 150 may be, for example, in operative communication with the temperature sensor 152 and the system 120, including the valve 158 and the compressor 122 (as indicated by the dashed lines in FIG. 2), such that the controller 150 may implement any suitable control logic for varying the ratio of refrigerant flow through the first and second condensers 124, 126 using the valve 158. Moreover, the controller 150 may selectively activate and control the system 120 in order to heat water within the interior volume 114 of the tank 112.

The controller 150 includes memory and one or more processing devices such as microprocessors, CPUs or the like, such as general or special purpose microprocessors operable to execute programming instructions or micro-control code associated with operation of the water heater appliance 100. The memory may represent random access memory such as DRAM, or read only memory such as ROM or FLASH. The processor executes programming instructions stored in the memory. The memory maybe a separate component from the processor or may be included onboard within the processor. Alternatively, the controller 150 may be constructed without using a microprocessor, e.g., using a combination of discrete analog and/or digital logic circuitry (such as switches, amplifiers, integrators, comparators, flip-flops, AND gates, and the like) to perform control functionality instead of relying upon software.

With reference now to FIG. 3, a flow diagram of an exemplary method (200) of operating a water heater appliance is provided. The method (200) includes, for example, flowing a refrigerant through a compressor at (202). From the compressor, the method (200) includes at (204) flowing a first portion of the refrigerant from the compressor through a first condenser and at (206) flowing a second portion of the refrigerant from the compressor through a second condenser. The first and second condensers may each be operable to heat water within the interior volume of the tank of the water heater appliance. Additionally, the first condenser and the second condenser may be configured in parallel flow with one another. At (208) the method (200) further includes flowing the refrigerant from the first condenser and from the second condenser through a valve in fluid communication with the first condenser and the second condenser, and at (210) flowing the refrigerant from the valve through an expansion device and through an evaporator. The valve is therefore positioned downstream from the first and second condensers.

It should be appreciated, however, that in other exemplary aspects of the method (200) of FIG. 3, the valve may instead be positioned upstream of the first and second condensers, and thus the method (200) may instead include flowing the refrigerant from the valve to and through the first and second condensers, and flowing the refrigerant from the first and second condensers through an expansion device and an evaporator.

Referring still to the exemplary method (200) of FIG. 3, the method (200) includes at (212) varying a ratio of refrigerant flow through the first condenser and through the second condenser using the valve. The valve may be configured in the same manner as the valve 158 discussed above with reference to FIG. 2, and similarly, the first and second condensers may also be configured in the same manner as the first and second condensers 124, 126 discussed above with reference to FIG. 2. Accordingly, the step of varying a ratio of refrigerant flow through the first condenser and through the second condenser using the valve at (212) may be performed by a processor of the water heater appliance.

In certain exemplary aspects, the exemplary method (200) may further include determining a temperature of the water within the inner volume of the tank of the water heater appliance. Such an exemplary method may further determine a volume of hot water in the tank based on the temperature measurement. For example, in certain embodiments, one or more of the methods disclosed in U.S. patent application Ser. No. 14/295,800 may be used to determine the volume of hot water in the tank based on the temperature measurement. The disclosure in U.S. patent application Ser. No. 14/295,800 is hereby incorporated fully by reference. Further, in such an exemplary aspect, varying the ratio of refrigerant flow through the first condenser and through the second condenser at (212) may be performed in response to the determined temperature of the water within the inner volume of the tank of the water heater appliance. Moreover, in still other exemplary aspects, the exemplary method (200) may further include determining a flow rate of water to and/or from the tank through, e.g., cold and hot water conduits. In such an exemplary aspect, varying the ratio of refrigerant flow through the first condenser and through the second condenser at (212) may be performed in response to the determined flow rate of water to and/or from the tank.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 

What is claimed is:
 1. A water heater appliance comprising: a tank defining an interior volume; and a sealed system for heating water within the interior volume of the tank, the sealed system comprising a compressor operable to compress a refrigerant; a first condenser positioned downstream of and in fluid communication with the compressor; a second condenser positioned downstream of and in fluid communication with the compressor, the first and second condensers each operable to heat water within the interior volume of the tank using energy from the refrigerant; and a valve in fluid communication with the first condenser and the second condenser and configured to vary a ratio of refrigerant flow through the first condenser and through the second condenser.
 2. The water heater appliance of claim 1, wherein the first condenser is configured in parallel flow with the second condenser.
 3. The water heater appliance of claim 1, wherein the water heater appliance defines a vertical direction, and wherein the first condenser is positioned above the second condenser along the vertical direction.
 4. The water heater appliance of claim 1, wherein the first condenser and the second condenser each surround the tank.
 5. The water heater appliance of claim 1, wherein the water heater appliance defines a vertical direction, wherein the tank comprises an upper portion and a lower portion each positioned along the vertical direction, and wherein the first condenser surrounds the upper portion and the second condenser surrounds the lower portion.
 6. The water heater appliance of claim 1, wherein the valve is positioned downstream from the first condenser and downstream from the second condenser.
 7. The water heater appliance of claim 1, wherein the valve is positioned upstream from the first condenser and upstream from the second condenser.
 8. The water heater appliance of claim 1, wherein the valve is a three-way valve utilizing a stepper motor.
 9. The water heater appliance of claim 1, wherein the valve comprises a first port in fluid communication with the first condenser, a second port in fluid communication with the second condenser, and a third port in fluid communication with the compressor or an expansion device.
 10. The water heater appliance of claim 1, further comprising a casing extending around at least a portion of the tank, wherein the valve is positioned within the casing.
 11. The water heater appliance of claim 10, wherein the compressor, the first condenser, and the second condenser are each positioned within the casing.
 12. The water heater appliance of claim 1, further comprising a hot water conduit and a cold water conduit each extending into the interior volume of the tank, the cold water conduit having a length within the interior volume greater than a length of the hot water conduit within the interior volume.
 13. A method for operating a water heater appliance, the method comprising: flowing a refrigerant through a compressor; flowing a first portion of the refrigerant from the compressor through a first condenser operable to heat water within an interior volume of a tank of the water heater appliance; flowing a second portion of the refrigerant from the compressor through a second condenser operable to heat water within the interior volume of the tank of the water heater appliance; and varying a ratio of refrigerant flow through the first condenser and through the second condenser using a valve in fluid communication with the first condenser and the second condenser.
 14. The method of claim 13, further comprising flowing the refrigerant from the first condenser and from the second condenser through the valve.
 15. The method of claim 13, further comprising flowing the refrigerant from the valve through the first condenser and through the second condenser.
 16. The method of claim 13, wherein the first condenser is configured in parallel flow with the second condenser.
 17. The method of claim 13, further comprising flowing the refrigerant from the first condenser and from the second condenser through an expansion device.
 18. The method of claim 13, wherein the tank comprises an upper portion and a lower portion each defined along a vertical direction, and wherein the first condenser surrounds the upper portion and the second condenser surrounds the lower portion.
 19. The method of claim 13, wherein the water heater appliance further comprises a casing surrounding at least a portion of the tank, and wherein the valve and the condenser are positioned within the casing.
 20. The method of claim 13, further comprising determining a temperature of the water within the inner volume of the tank of the water heater appliance, and wherein said step of varying the ratio of refrigerant flow through the first condenser and through the second condenser is performed in response to the determined temperature of the water within the inner volume of the tank of the water heater appliance. 